Touch panels can be classified according to the position sensing method into an optical type, an ultrasonic type, a capacitive type, a resistive film type, and the like. In particular, the resistive film type has a simple structure and thus is cost-effective so that it has come into wide use in recent years. For example, resistive film type touch panels are used for automatic teller machines (ATMs) in banks and for display panels of transportation ticket machines and the like.
The resistive film type touch panels are configured to include a transparent conductive laminate and a transparent conductive thin film-attached glass member that are opposed to each other with a spacer interposed therebetween, in which an electric current is allowed to flow through the transparent conductive laminate, while the voltage at the transparent conductive film-attached glass member is measured. When the transparent conductive laminate is brought into contact with the transparent conductive film-attached glass member by pressing with a finger, a pen or the like, the electric current flows through the contact portion so that the position of the contact portion is detected.
In recent years, the market for touch panels to be installed in smartphones, personal digital assistances (PDAs), game computers, and the like is expanding, and the frame part of touch panels becomes narrower. This increases the opportunity to push touch panels with fingers so that not only requirements for pen input durability but also requirements for surface contact pressure durability should be satisfied.
For example, it is disclosed that the touch panel includes a transparent film substrate and an anchor layer, a SiOx layer, and a transparent conductive layer that are provided on at least one side of the transparent film substrate, wherein the anchor layer is made of a resin containing at least fine particles with an average particle size of 1 to 30 nm and has a center line average roughness Ra of 4 to 20 nm (see Patent Document 1 listed below). However, this structure has the problem of lack of reliability, because the surface resistance of the transparent conductive layer is variable.
It is also disclosed that the touch panel includes a transparent conductive film in which a substrate, an anchor layer, and a conductive layer are sequentially stacked, and the anchor layer serves to anchor the conductive layer (see Patent Document 2 listed below). Patent Document 2 discloses that the anchor layer is a silica layer formed by a plasma CVD method. According to the invention described in Patent Document 2, however, durability against surface contact pressure (surface contact pressure durability) is insufficient, although it is disclosed that the invention can provide a pen-input touch panel or the like that can sufficiently withstand application of a large sliding load.
Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2002-117724
Patent Document 2: JP-A No. 2003-320609